This invention relates generally to ridable bouncing apparatuses and more particularly to such apparatuses which achieve high performance, have radically adjustable spring strength or which employ compound elastomer springs or enclosed thrust assemblies. The invention also relates to ridable bouncing apparatuses that provide features for convenient engagement and disengagement of springs/tension elements, as well as semi-mounted internal storage of the springs/tension elements.
Steel-spring pogo sticks are the dominant form of ridable bouncing apparatus, and forms are known which aspire to high performance or adjustability or which have enclosed springs. High performance (that is, energy storage and return in the kilojoule range) is problematic for steel spring devices because the storage capacity of the material is low: about 80 joules/kilogram. 1000 joules of storage thus requires about 12 kilograms (26 pounds) of spring. An apparatus of such weight would be unwieldy, unappealing and hazardous due to its own momentum. Manufacturers have stopped at about one-third of this level (which still makes for a rather heavy apparatus). A group of engineering students at the Oregon Institute of Technology, however, has produced a pogo stick with a 47-inch custom-made steel spring intended to propel 250 pounds to a height of 5 feet (implying a capacity of 1700 joules, and a spring weight approaching 40 pounds). Their attained height is 18 inches; they express disappointment, and blame the unwieldiness of the design.
No radically-adjustable steel-spring pogo is known, although devices which suggest such a development were discussed as early as 1881. For example, U.S. Pat. No. 438,830 to Yagn in 1890 discloses compound-coil-spring jumping stilts. Several designs which precompress a coil spring to effect a form of adjustability have been presented, for example, in U.S. Pat. No. 238,042 to Herrington in 1881; U.S. Pat. No. 2,793,036 to Hansburg in 1957; and U.S. Pat. No. 3,773,320 to Samiran et al. in 1973. Such pre-compression does not scale the spring (that is, change its strength), and is of little mechanical significance.
Pogo sticks with enclosed coil springs are shown by Hohberger (U.S. Pat. No. 2,712,443 in 1955), Rapaport (U.S. Pat. No. 2,871,016 in 1957) and Gaberson (U.S. Pat. No. 3,116,061 in 1963). Hohberger assembles his molded frame permanently around the coil. Rapaport places a flexible plastic cover around the spring. Gaberson places the spring inside the piston, and adds a frame-attached plunger to compress it. All of these designs are limited by the modest capacity of their steel springs.
Air-spring pogo sticks have achieved commercialization using low-pressure air springs, the air being contained either in a ball-like bladder or in a block of low-density plastic foam. Such devices are successful as children's novelties but are not well-suited to more demanding applications due to the bulk of the entrapped air column. High pressure air springs are theoretically capable of achieving any desired level of performance, and also hold the promise of straightforward adjustability. Their use in pogo sticks was suggested by Woodall (U.S. Pat. No. 2,865,633 in 1958), who stressed the benefit of adjustability, and others (Bourcier de Carbon in U.S. Pat. No. 2,899,685 in 1959; Guin in U.S. Pat. No. 3,351,342 in 1967). There is, however, a practical problem: the energy stored is present in the form of heat at the bottom of the stroke—and due to the relatively large amount of energy and relatively small amount of gas, temperatures of several hundreds of degrees are attained. A leading manufacturer has told me of experiments which ended in dismay when the cylinder became hot enough to burn the jumpers' legs.
Elastomer-powered pogo designs appear in Gaffney and Weaver (in U.S. Pat. No. 2,783,997 in 1957). Their primary concern was with jumping stilts; their pogo design was minimally modified from a conventional tubular design, and had its rubber mounted externally in two bundles, one on either side of the frame tube. These bundles would have made the upper mount about three inches wide—and this unshielded object would rake up and down between the knees and thighs of the jumper on each stroke; if the rider attempted to ride bowlegged to avoid it, his contact with and ability to control the stick (as well as his concentration) would suffer.
Bourcier de Carbon (cited above) shows an elastomer-powered stilt, and appears to be the first in this context to mention that rubber is a more efficient spring material than steel and can provide higher levels of performance. His upper mount is exposed, which is viable for a stilt; he does not show a ridable design.
Hoffmeister (U.S. Pat. No. 3,065,962 in 1962) gives a quantitative statement of the startling superiority of rubber: 18 pounds of steel, he points out, can be replaced by 3.75 ounces of rubber. His mechanical design (which is for jumping stilts), however, is extraordinarily unsafe. He attaches the bottom of the tension spring to the top of the frame tube (rather than the bottom, as shown by Gaffney and Bourcier de Carbon). This results in rod ends projecting past the rider's knees and moving upward relative to the rider as he lands. A jumper landing in a skier's tuck position will strike the ends of the piston rods with his chest at up to 11 mph.
Prueitt (U.S. Pat. No. 4,449,256 in 1984) cites the scalability of rubber-band springs as a virtue of his design. The design is for multi-piston jumping stilts with exposed piston-heads.
In the past, it has been difficult to perform adjustments on bouncing apparatuses. For instance, a user might have to take the apparatus completely apart in order to make adjustments to the spring or other tension element. Therefore, it is desirable to provide convenient access to these and other components that are inside the bouncing apparatus.
Furthermore, a need exists for a relatively large disk foot for use in high-performance pogo sticks. Two university projects have striven for record-setting pogo performance, and both have adopted disk feet. The developers of the BowGo at Carnegie Mellon University have used a disk rigidly mounted on the piston, with a convex rubber pad on the bottom. While this system may permit the BowGo to be used on a lawn, it does little to accommodate uneven ground or tilting of the pogo, and does not distribute the load uniformly over the surface of the disk. A project at the Oregon Institute of Technology has employed a disk foot mounted on a ball joint. While such a system may provide adequate pressure distribution and can accommodate pogo tilts and uneven ground, the ball joint permits the foot to rotate relative to the shaft. Thus, it has little capacity to transmit torque, and will not enable aggressive yaw maneuvers such as, e.g., aerial spins.
Therefore, there is a need for a bouncing apparatus capable of unprecedented performance.
There is also a need for a bouncing apparatus having a thrust function that can be scaled to match the weights and inclinations of a broad range of rider sizes, thus affording each rider an optimal apparatus that exploits the travel available in its linkage.
There is also a need for a bouncing apparatus that shields the rider from the moving parts of the apparatus during operation, but permits convenient access to tension elements for adjustment of spring strength.
There is also a need for a bouncing apparatus having a foot that is capable of tilting in any direction without rotating, and that can be used on soft surfaces such as lawns, and that can offer improved traction on hard surfaces.
There is also a need for a bouncing apparatus with a spring that can conveniently be pre-tensioned for use and relaxed for storage. Similarly, there is also a need to store the spring or tension element internally within the bouncing apparatus in an untensioned semi-mounted fashion.
There is also a need for a bouncing apparatus having a cartridge unit structure that permits convenient removal from the apparatus to allow a user to perform adjustments on tension elements or other components.
Furthermore, there is also a need for a bearing that can transmit torque, so that torque exerted by a rider on the assembly does not cause the carriage to rotate around the piston but rather transmits the torque to the piston.
Springs/tension elements that are overstretched or are load bearing for long periods of time tend to become permanently elongated (“elongation set”). For example, in experiments on speargun bands, which often consist of rubber bands as the tension component for propelling the spear projectile, at least one researcher has found a 10% elongation on bands after one hour at 300% elongation. It is also well known that many elastomeric materials “creep” or relax over time. Natural rubbers may creep on the order of 1.5% per decade of time. Thermoplastic polymers may creep up to 8% per decade. Unfortunately, an overstretched or relaxed spring/tension element may result in a loss of clearance between disengaged elements and the mounts that are used when the elements are engaged and operational. Furthermore, such improperly tensioned components may cause hazardous conditions during operation of the apparatus. Thus, there is a need to address creeping and overstretching.
Another issue concerning the spring/tension element occurs when a cap or end piece is attached to it. Over time, the connection between the spring/tension element and the cap/end piece may fail. This may cause a hazardous condition, and may also require repairs or replacements, which add unwanted costs. Thus, there is a need form improved techniques of attach caps and end pieces to springs and tension elements so that there is an extended lifespan and/or a reduced failure rate.